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  Subjects -> ENGINEERING (Total: 2235 journals)
    - CHEMICAL ENGINEERING (188 journals)
    - CIVIL ENGINEERING (178 journals)
    - ELECTRICAL ENGINEERING (102 journals)
    - ENGINEERING (1194 journals)
    - ENGINEERING MECHANICS AND MATERIALS (374 journals)
    - HYDRAULIC ENGINEERING (54 journals)
    - INDUSTRIAL ENGINEERING (60 journals)
    - MECHANICAL ENGINEERING (85 journals)

CHEMICAL ENGINEERING (188 journals)                  1 2     

AATCC Journal of Research     Full-text available via subscription   (Followers: 4)
ACS Sustainable Chemistry & Engineering     Hybrid Journal  
Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials     Hybrid Journal   (Followers: 6)
Acta Polymerica     Hybrid Journal   (Followers: 7)
Additives for Polymers     Full-text available via subscription   (Followers: 20)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 5)
Advanced Chemical Engineering Research     Open Access   (Followers: 11)
Advanced Powder Technology     Hybrid Journal   (Followers: 16)
Advances in Applied Ceramics     Partially Free   (Followers: 3)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 18)
Advances in Chemical Engineering and Science     Open Access   (Followers: 26)
Advances in Polymer Technology     Hybrid Journal   (Followers: 11)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 5)
Annual Review of Analytical Chemistry     Full-text available via subscription   (Followers: 9)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 10)
Anti-Corrosion Methods and Materials     Hybrid Journal   (Followers: 4)
Applied Petrochemical Research     Open Access   (Followers: 3)
Asia-Pacific Journal of Chemical Engineering     Hybrid Journal   (Followers: 6)
Biochemical Engineering Journal     Hybrid Journal   (Followers: 9)
Biofuel Research Journal     Open Access   (Followers: 3)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 8)
Brazilian Journal of Chemical Engineering     Open Access   (Followers: 3)
Bulletin of Chemical Reaction Engineering & Catalysis     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 3)
Carbohydrate Polymers     Hybrid Journal   (Followers: 9)
Catalysts     Open Access   (Followers: 8)
ChemBioEng Reviews     Full-text available via subscription  
Chemical and Engineering News     Free   (Followers: 7)
Chemical and Materials Engineering     Open Access   (Followers: 2)
Chemical and Petroleum Engineering     Hybrid Journal   (Followers: 11)
Chemical and Process Engineering     Open Access   (Followers: 4)
Chemical and Process Engineering Research     Open Access   (Followers: 6)
Chemical Communications     Full-text available via subscription   (Followers: 37)
Chemical Engineering & Technology     Hybrid Journal   (Followers: 25)
Chemical Engineering and Processing: Process Intensification     Hybrid Journal   (Followers: 10)
Chemical Engineering and Science     Open Access   (Followers: 3)
Chemical Engineering Communications     Hybrid Journal   (Followers: 11)
Chemical Engineering Journal     Hybrid Journal   (Followers: 24)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 19)
Chemical Engineering Research Bulletin     Open Access   (Followers: 1)
Chemical Engineering Science     Hybrid Journal   (Followers: 18)
Chemical Geology     Hybrid Journal   (Followers: 11)
Chemical Papers     Hybrid Journal   (Followers: 3)
Chemical Product and Process Modeling     Hybrid Journal   (Followers: 3)
Chemical Reviews     Full-text available via subscription   (Followers: 128)
Chemical Society Reviews     Full-text available via subscription   (Followers: 37)
Chemical Technology     Open Access   (Followers: 5)
ChemInform     Hybrid Journal   (Followers: 3)
Chemistry & Industry     Hybrid Journal   (Followers: 2)
Chemistry Central Journal     Open Access   (Followers: 7)
Chemistry of Materials     Full-text available via subscription   (Followers: 132)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 8)
ChemSusChem     Hybrid Journal   (Followers: 8)
Chinese Chemical Letters     Full-text available via subscription   (Followers: 3)
Chinese Journal of Chemical Engineering     Full-text available via subscription   (Followers: 3)
Chinese Journal of Chemical Physics     Hybrid Journal   (Followers: 2)
Coke and Chemistry     Hybrid Journal  
Coloration Technology     Hybrid Journal   (Followers: 1)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 9)
Computer Aided Chemical Engineering     Full-text available via subscription   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 8)
CORROSION     Full-text available via subscription   (Followers: 18)
Corrosion Engineering, Science and Technology     Hybrid Journal   (Followers: 38)
Corrosion Reviews     Hybrid Journal   (Followers: 5)
Crystal Research and Technology     Hybrid Journal   (Followers: 2)
Current Opinion in Chemical Engineering     Open Access   (Followers: 3)
Education for Chemical Engineers     Hybrid Journal   (Followers: 4)
Eksergi     Open Access  
Emerging Trends in Chemical Engineering     Full-text available via subscription  
European Polymer Journal     Hybrid Journal   (Followers: 44)
Fibers and Polymers     Full-text available via subscription   (Followers: 3)
Fluorescent Materials     Open Access   (Followers: 1)
Focusing on Modern Food Industry     Open Access   (Followers: 3)
Frontiers of Chemical Science and Engineering     Hybrid Journal   (Followers: 1)
Gels     Open Access  
Geochemistry International     Hybrid Journal  
Handbook of Powder Technology     Full-text available via subscription   (Followers: 3)
Heat Exchangers     Open Access   (Followers: 1)
High Performance Polymers     Hybrid Journal  
Hungarian Journal of Industry and Chemistry     Open Access  
Indian Chemical Engineer     Hybrid Journal   (Followers: 4)
Indian Journal of Chemical Technology (IJCT)     Open Access   (Followers: 11)
Indonesian Journal of Chemical Science     Open Access  
Industrial & Engineering Chemistry     Full-text available via subscription   (Followers: 10)
Industrial & Engineering Chemistry Research     Full-text available via subscription   (Followers: 20)
Industrial Chemistry Library     Full-text available via subscription   (Followers: 4)
Info Chimie Magazine     Full-text available via subscription   (Followers: 2)
International Journal of Chemical and Petroleum Sciences     Open Access   (Followers: 2)
International Journal of Chemical Engineering     Open Access   (Followers: 7)
International Journal of Chemical Reactor Engineering     Hybrid Journal   (Followers: 3)
International Journal of Chemical Technology     Open Access   (Followers: 4)
International Journal of Chemoinformatics and Chemical Engineering     Full-text available via subscription   (Followers: 2)
International Journal of Food Science     Open Access   (Followers: 4)
International Journal of Industrial Chemistry     Open Access  
International Journal of Polymeric Materials     Hybrid Journal   (Followers: 4)
International Journal of Science and Engineering     Open Access   (Followers: 7)
International Journal of Waste Resources     Open Access   (Followers: 5)
Journal of Chemical Engineering & Process Technology     Open Access   (Followers: 3)
Journal of Applied Crystallography     Hybrid Journal   (Followers: 5)
Journal of Applied Electrochemistry     Hybrid Journal   (Followers: 11)

        1 2     

Journal Cover Chemical Engineering Science
  [SJR: 1.178]   [H-I: 114]   [18 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0009-2509
   Published by Elsevier Homepage  [2801 journals]
  • Liquid hold-up and gas–liquid mass transfer in an alumina open-cell
           foam
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): Rita R. Zapico, Pablo Marín, Fernando V. Díez, Salvador Ordóñez
      Open-cell foams are solid structures formed by an intricate network of macroporous interconnected channels. The high porosity and tortuosity of the channels results in high external surface area, so open-cell foams are very efficient for promoting phase contact, e.g. in gas–liquid packed-bed reactors. In addition, the tortuous path of the channels breaks up the flow and enhances mass transfer with respect to other structured beds, such as honeycomb monoliths, and pressure drop is comparatively low. The liquid hold-up (system water–air), and the mass transfer coefficient (oxygen from water to nitrogen), have been measured for a ceramic foam, specifically a 20ppi alumina foam bed of 50mm diameter and 100mm length (average pore diameter 1.25mm and strut diameter 0.42mm), for co-current down flow. Gas and liquid flow rates have been varied in the range corresponding to 0–8.5·10−2 and 0–3.2·10−3 m/s superficial velocities, respectively. At these conditions, the bed operates at trickle flow regime. The dynamic liquid hold-up and the mass transfer coefficient have been correlated as a function of relevant dimensionless numbers.


      PubDate: 2016-02-01T03:26:17Z
       
  • Visualization and characterization of gas–liquid mass transfer
           around a Taylor bubble right after the formation stage in microreactors
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): Lixia Yang, Nicolas Dietrich, Karine Loubière, Christophe Gourdon, Gilles Hébrard
      The gas–liquid mass transfer occurring in Taylor flows right after the bubble formation stage were investigated in a flow-focusing microreactor. The colorimetric technique proposed by Dietrich et al. (2013) was used for locally visualizing and characterizing the gas–liquid mass transfer. Thanks to this method, the liquid-side mass transfer coefficients k L were measured at the moment right after the bubble is detaching from the gas film near the cross-junction of the microreactor. Experiments were carried out for several flow conditions ( 95 . 7 < Re < 226 . 1 , 0 . 0043 < Ca < 0 . 010 , 0 . 4 < We < 2 . 3 , Bo = 0 . 044 ) and bubble size (2.34<L b /l<5.59). The results have demonstrated that the contribution of mass transfer right after the bubble formation stage is reasonably larger to those obtained at the bubble flowing-stage.


      PubDate: 2016-02-01T03:26:17Z
       
  • Development of an endoscopic-laser PIV/DIA technique for high-temperature
           gas–solid fluidized beds
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): I. Campos Velarde, F. Gallucci, M. van Sint Annaland
      To enable the investigation of the hydrodynamics of gas–solid fluidized bed reactors at high-temperatures and reactive conditions, a new non-invasive experimental technique has been developed, based on the extension of Particle Image Velocimetry (PIV) coupled with Digital Image Analysis (DIA) using dedicated high-temperature endoscopes for image recording and laser illumination. The new endoscopic-laser PIV/DIA technique (ePIV/DIA) allows to determine simultaneously information from the emulsion and bubble phase with high spatial and temporal resolution in a pseudo-2D columns. The ePIV/DIA technique with single-source laser illumination has first been thoroughly validated at cold-flow conditions by comparison with a standard PIV/DIA technique with LED-illumination, showing very good agreement of the results in terms of particle velocity and solids mass flux profiles. The technique has subsequently been applied to fluidized beds in the bubbling fluidization regime at elevated temperatures to demonstrate its unique possibilities to measure detailed bed hydrodynamics at elevated temperatures.
      Graphical abstract image

      PubDate: 2016-02-01T03:26:17Z
       
  • Filtered model for the cold-model gas–solid flow in a large-scale
           MTO fluidized bed reactor
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): Li-Tao Zhu, Le Xie, Jie Xiao, Zheng-Hong Luo
      In this work, a three-dimensional (3-D) filtered two-fluid model (TFM) was developed to describe the gas–solid flow behavior in a large-scale methanol-to-olefins (MTO) fluidized bed reactor (FBR). The cold-model flow behaviors were characterized successfully via the filtered TFM with a coarse grid. A coarse-grid sensitivity test was first carried out, and the filtered model was testified using predictions from classical models and the experimental data. Moreover, four drag models have been incorporated into the TFM for evaluating the effectiveness of these models at the same coarse-grid condition. Subsequently, the effects of some important model parameters including solid stresses, wall corrections and filter size on the flow behaviors were also investigated numerically. Finally, the filtered model was applied to predict the effects of the operating gas velocity, distributor shape and solid particle size. The results suggested the effectiveness of the sub-grid models for simulating large-scale MTO FBRs at coarse-grid conditions. This study further confirmed that the filtered drag coefficient correlation plays a significant role in capturing flow behaviors and the filter size is nearly independent on the grid size when the filter size is larger than or equal to twice the grid size. The simulation results by coarse-grid also show that the catalyst particles are easier to be fluidized with the increase of the operating gas velocity. It is also found that a triangle-shaped distributor strengthens the mixing behaviors and weakens the clustering of the near-wall regions. Additionally, our study indicates that the clustering phenomena near the wall regions are more obvious with the decrease of the catalyst particle size.
      Graphical abstract image

      PubDate: 2016-02-01T03:26:17Z
       
  • Speeding up CFD simulation of fluidized bed reactor for MTO by coupling
           CRE model
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): Bona Lu, Hao Luo, Hua Li, Wei Wang, Mao Ye, Zhongmin Liu, Jinghai Li
      The methanol to olefins (MTO) process opens an economical and important route to produce light olefins. The design of MTO reactor borrows ideas from the reaction–regeneration configuration of the modern fluid catalytic cracking (FCC) units. However, their hydrodynamic behaviors are quite different in the sense that the fluidized bed for MTO reactions operates in different flow regime from that of FCC, calling for new modeling for scale-up. In addition, the coke deposited on catalysts greatly affects the MTO reaction while its generation is very slow. It normally takes tens of minutes or even hours for catalysts to reach the desired level of coke content. Time-dependent computational fluid dynamics (CFD) simulation of such a long process poses a big challenge to reactive multiphase flow modeling. To speed up it, we try to integrate the classic chemical reaction engineering (CRE) model with CFD. In particular, the continuous stirred tank reactor (CSTR) model is established to estimate the steady state distribution of coke content, which is then set as the initial distribution for CFD simulation to shorten the time to reach the steady state of reactive flows. Comparison with experimental data shows good agreement and also great speed-up ratio compared to traditional CFD simulation.


      PubDate: 2016-02-01T03:26:17Z
       
  • CFD simulations of shell-side flow in a shell-and-tube type heat exchanger
           with and without baffles
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): Eshita Pal, Inder Kumar, Jyeshtharaj B. Joshi, N.K. Maheshwari
      Shell-and-tube heat exchanger has been extensively used in industrial and research fronts for more than a century. However, most of its design procedures are based on empirical correlations extracted from experimental data of long length shell and tube heat exchanger. In this paper, an attempt has been made to investigate the complex flow and temperature pattern in such a short shell and tube type heat exchanger, with and without baffles in the shell side. Heat exchangers of length by hydraulic diameter ratio between 7 < L / D h < 21 ( 0.15 m < D S < 0.6 m ) for unbaffled and L / D h < 7 ( D S = 0.09 m ) for baffled heat exchangers are analysed using CFD code OpenFOAM-2.2.0 for different mass flow rates. It was observed that the cross flow near the nozzle region has a significant contribution towards the heat transfer, hence the conventional heat transfer correlations do not apply to these short heat exchangers. Furthermore, a sensitivity study of turbulence models was performed and it was observed that the standard k – ε model gives best results for the velocity profile as well as heat transfer, provided average y + of the first node adjacent to the heat transfer surface is maintained greater than 15. The commonly used boundary conditions at the exit are not realistic, as it tends to give either incorrect flow and temperature fields, or the solution was found to diverge. Through a sensitivity study of the exit length, it was found that exit length to shell side velocity ratio of 2.5 is required for proper convergence. Finally the effect of flow field on shell side heat transfer coefficient and a comparison with analytical methods are presented.


      PubDate: 2016-02-01T03:26:17Z
       
  • Mass transfer limitations in a monolithic reactor for the catalytic
           oxidation of ethanol
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): M.L. Rodríguez, L.E. Cadús
      A theoretical study of a monolithic reactor for the catalytic oxidation of Volatile Organic Compounds (VOC) over manganese–copper mixed oxide catalysts is presented. An isothermal one-dimensional heterogeneous model is selected to account for the external (gas–solid) and internal (washcoat) mass transport limitations. The results reveal that under certain operating conditions, e.g. thick washcoats and high conversions of VOCs (high temperatures), the overall process rate is reduced by internal diffusion inside the catalyst. At high temperatures and/or monoliths with poor interfacial areas, the overall process rate is limited by external mass transfer resistance to the catalyst. Proper quantification of both internal and external mass transfer resistances by means of a heterogeneous model can result in avoiding situations of incomplete VOC abatement under conditions of high VOC dilution.
      Graphical abstract image

      PubDate: 2016-02-01T03:26:17Z
       
  • Probing the effect of nanotubes on N-nitrosodimethylamine photocatalytic
           degradation efficiency and reaction pathway
    • Abstract: Publication date: 22 April 2016
      Source:Chemical Engineering Science, Volume 144
      Author(s): Xiaoyan Guo, Huaiqi Shao, Lulu Kong, Mingce Long, Man Zhang, Qixing Zhou, Wanli Hu
      Degradation efficiency, product distribution and reaction pathway of N-nitrosodimethylamine (NDMA) photocatalytic degradation over TiO2 nanotube(TiNT), Au-modified TiO2 nanotube(Au/TiNT) and TiO2 nanopowder(TiO2) were investigated to evaluate the tube effect. The results show that TiO2 nanotube was prepared and tubular morphology was kept after Au modification. The degradation efficiencies of NDMA over TiNT and Au/TiNT are significantly higher than that over TiO2 powder, DMA becomes to be the major product, and NO2 − production is also detectable, which all stem from the tubular morphology of TiNT and Au/TiNT. In the presence of TiNT and Au/TiNT, the small NDMA molecules enter into the nanotube and lead to a higher concentration and a closer contact in a nanotube structure space, resulting in remarkable high degradation efficiencies of NDMA, and also initiating new photocatalytic reaction pathway derived from effectively contacts between radical intermediate and NO2 − products in the nanotube structure. The nanotubular morphology of TiNT and Au/TiNT plays an important role in enhancing NDMA photocatalytic performances.
      Graphical abstract image

      PubDate: 2016-02-01T03:26:17Z
       
  • Structural changes in casein aggregates under frozen conditions affect the
           entrapment of hydrophobic materials and the digestibility of aggregates
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): Kyuya Nakagawa, Teeraya Jarunglumlert, Shuji Adachi
      Freeze-dried casein nanoparticles that could entrap β-carotene were produced after aging under frozen conditions. Structural changes that occurred during aging and simulated digestion were investigated. Freeze-dried specimens of casein particles prepared from sodium caseinate solutions containing dispersed β-carotene successfully entrapped this dispersion in the resulting freeze-dried powders. The entrapped β-carotenes were distributed between the surface (surface load) and interior (inner load) of these dried powders. Because of aging, the amount of the inner load decreased while the surface load simultaneously increased. The hydrophobicity of rehydrated casein particles indicated that a change, caused by the aging process, occurred in particle structure. These structural modifications increased the hydrophobicity in the dried specimens. When rehydrated, these hydrophobic surfaces reassociated with each other to cancel the net gain in hydrophobicity. SAXS measurements on freeze-thawed casein nanoparticles also suggested the formation of modified nano- and microstructures. These modified structures were formed by freezing and thawing, along with interactions between clusters or between clusters and ice. The kinetics of the proteolytic reactions of the freeze-thawed specimens in a simulated gastric fluid were measured. The degree of aggregation and processing conditions did not significantly affect the digestion kinetics of the casein clusters. The SAXS analyses, however, suggested that these conditions affected nano- and microstructure formation during digestion. When the aggregated casein clusters were exposed to the gastric conditions, the fractured clusters produced by the proteolytic reactions produced 2–3 times larger aggregates with hollow networks and rough surfaces created by the crosslinked casein clusters. Processing conditions, such as pH and aging time, likely affected these nano- and microstructure formations under gastric conditions. These results may provide exciting future research opportunities if the structural modifications can impact the bioavailability of entrapped materials.


      PubDate: 2016-02-01T03:26:17Z
       
  • Intensified Eu(III) extraction using ionic liquids in small channels
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): Qi Li, Panagiota Angeli
      The extraction of Eu(III) from nitric acid solutions was studied in intensified small scale separation units using an ionic liquid solution (0.2M n-octyl(phenyl)-N,N-diisobutylcarbamoylmethyphosphine oxide (CMPO)–1.2M Tributylphosphate) (TBP)/1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]amide; ([C4min][NTf2])as the extraction phase. The investigations were carried out in channels with 0.2mm and 0.5mm diameter for phase flowrates that result in plug flow with the aqueous solution as the dispersed phase. The interfacial area in plug flow and the velocity profiles within the plugs were studied with high speed imaging and bright field micro Particle Image Velocimetry. Distribution and mass transfer coefficients were found to have maximum values at nitric acid concentration of 1M. Mass transfer coefficients were higher in the small channel, where recirculation within the plugs and interfacial area are large, compared to the large channel for the same mixture velocities and phase flow rate ratio. Within the same channel, mass transfer coefficients decreased with increasing residence time indicating that significant mass transfer takes place at the channel inlet where the two phases come into contact. The experimental results were compared with previous correlations on mass transfer coefficients in plug flows.


      PubDate: 2016-01-28T08:44:39Z
       
  • Process development for the synthesis of saturated branched fatty
           derivatives: Combination of homogeneous and heterogeneous catalysis in
           miniplant scale
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): J. Haßelberg, A. Behr, C. Weiser, J.B. Bially, I. Sinev
      Saturated branched fatty derivatives find application in lubricant and cosmetic industry due to the decisive advantages in temperature and viscosity behavior compared to their linear homologs. Thus, finding new synthesis routes, particularly based on renewable resources, is of great industrial interest. This work covers a new synthesis route for production of such saturated branched derivatives based on linoleic methyl ester. The developed process combines homogeneously rhodium catalyzed co-oligomerization of linoleic methyl ester with ethylene and heterogeneously catalyzed hydrogenation of the co-oligomers in miniplant scale. The paper focuses on the hydrogenation in trickle bed reactor and optimization of operation conditions as well as optimization of packings and liquid distribution. Saturated branched derivatives with very low iodine values have been produced in miniplant scale using a diluted catalyst packing consisting of large Pd/C catalyst pellets and small SiC particles. Different SiC fractions have been tested to investigate the effect on liquid distribution. Additionally long term stability of the heterogeneous Pd/C catalyst has been successfully tested for more than 100h. Simultaneous adsorption of the used homogenous rhodium catalyst on the fixed bed was analyzed by XPS. Additionally this paper discusses the general transferability of the process combination consisting of homogeneous and heterogeneous reaction steps to other synthesis route and product groups.
      Graphical abstract image

      PubDate: 2016-01-28T08:44:39Z
       
  • Experimental and simulated solids mixing and bubbling behavior in a scaled
           two-section two-zone fluidized bed reactor
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): I. Julián, J. Herguido, M. Menéndez
      Digital Image Analysis techniques, a phenomenological Counter-Current Back-Mixing model (CCBM) and Two-Fluid Model (TFM) simulations were employed to evaluate the effect of scale on the Two-Section Two-Zone Fluidized Bed Reactors (TS-TZFBR) fluid dynamics, i.e. bubble characteristics, axial mixing of solids and defluidization phenomena. The reactor scaling did not affect the quality of the TFM bubble size predictions. A bubble size correlation previously proposed by the authors for TS-TZFBR units was able to predict the experimental axial bubble size evolution at the different reactor scales and gas velocities (ugas /umf =1.5–3.0) with a relative error under 17%. The TFM simulated axial solid mass fluxes were same order as these obtained by Particle Image Velocimetry for every reactor size. However, the classical CCBM model was unable to predict the effect of scale on the solids axial mixing in a TS-TZFBR. The inclination angle of the defluidized bed regions found within the TS-TZFBR tapered zone, β, increased by (ugas /umf )0.25 when duplicating the reactor size. Nevertheless, it did not exceed the prescribed upper limit of β=80° for any of the conditions tested.


      PubDate: 2016-01-28T08:44:39Z
       
  • Macroscopic and spectroscopic identifications of the synergetic inhibition
           of an ionic liquid on hydrate formations
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): Seong-Pil Kang, Taesung Jung, Jong-Won Lee
      In order to identify the synergetic inhibition of hydrate formation by a new pyrrolidinium cation-based ionic liquid with a commercial kinetic inhibitor, poly(N-vinylcaprolactam)(PVCap), pure CH4 (structure I) and synthesized natural gas (structure II) hydrate samples are prepared and analyzed with solid-state 13C NMR spectroscopy. In addition, the time-resolved macroscopic pressure changes and microscopic Raman spectra are also measured using the synthesized natural gas and two inhibitors. Hydrate formation or formed hydrate structure is found to be different for the PVCap-only and the PVCap + [HEMP][BF4] systems. Furthermore, the addition of [HEMP][BF4] is found to delay the induction time and hydrate growth further when added to the PVCap-only system although some deviations are observed for the induction time. Adding the ionic liquid to the PVCap system can have a synergetic effect on the hydrate formation (natural gas hydrate of the structure II, in particular), which may indicate different inhibition mechanisms of PVCap and [HEMP][BF4].
      Graphical abstract image

      PubDate: 2016-01-28T08:44:39Z
       
  • Thin film flow on a vertically rotating disc of finite thickness partially
           immersed in a highly viscous liquid
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): Md Salim Miah, Saphwan Al-Assaf, Xiaogang Yang, Alison McMillan
      The entrainment and flow of a thin film of liquid on a vertically rotating disc partially immersed in a liquid bath has been investigated experimentally and modelled numerically. The Volume of Fluid (VOF) Computational Fluid Dynamics (CFD) modelling approach has been employed to characterise the shape and stability of the thin film thickness profile. The thickness of the rotating disc plays a significant role in the thin film profile and this is confirmed through the comparison of simulation with the experimental results. Other factors determining the film thickness were identified as the rotational speed and the fluid viscosity where the film thickness profile increases with the increase of the rotational speed and also the viscosity. A correlation equation to predict the film thickness as a function of angular position, radius, rotating speed, viscosity and surface tension is proposed. The results given in this study specifically report on the thin film thickness variation with the angular direction and the film entrained into the liquid. In both the simulation and experimental results, it is noted that the film thickness stabilises following a rotation of 15° after drag out of the liquid, and remains so until 10° before being dragged back in.


      PubDate: 2016-01-21T18:21:44Z
       
  • Hydrodynamics and pressure loss of concurrent gas–liquid downward
           flow through sieve plate packing
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): Wangde Shi, Weixing Huang, Yuhan Zhou, Huan Chen, Dawei Pan
      Gas–liquid concurrent downward flow through a new structured packing was investigated by experiment systematically. The experimental packing consisted of 21 sieve plates. Each plate was 190mm×190mm in side length and 1mm in thickness. Three sets of packing with different sizes of sieve holes were tested. During experiment, four flow states have been observed, i.e., the trickling flow at low gas and liquid flux, the continuous flow at low gas but high liquid flux, the semi-dispersed flow at high gas flux and the completely dispersed flow as gas flux increases further. Another important phenomenon observed is the occurrence of pulsing flow, i.e., in some range of gas and liquid flow fluxes, both two phases will no longer flow smoothly through the sieve plates but flow downward in pulse regularly. Through extensive experiment, the rough boundaries for flow regime transition were obtained. Then, the pressure losses of gas flow and gas–liquid two phase flow in non-pulsing flow regime were systematically measured. The analysis for pressure differences measured at different locations show that for a given packing, the pressure loss through each plate is nearly the same. Its magnitude depends on the gas and liquid flow rates. The comparisons between pressure losses of different packings indicate that the pressure loss is associated with the hole diameter, hole pitch, free area ratio of sieve plate and the mounting distance between two adjacent plates. Finally, considering these factors, the correlations for pressure drops were developed, which approximates the experimental values with an average deviation less than 10%.


      PubDate: 2016-01-21T18:21:44Z
       
  • Graphene oxide incorporated thin-film composite membranes for forward
           osmosis applications
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): Liang Shen, Shu Xiong, Yan Wang
      In this work, graphene oxide (GO) nanosheets are synthesized and incorporated into the polyamide (PA) selective layer to develop a novel thin-film composite (TFC) membrane for forward osmosis (FO) application. The chemical structure and morphology of the synthesized GO and GO-incorporated TFC membranes are studied by various characterization techniques. Compared with the control TFC membrane, GO-incorporated TFC membranes exhibit higher water flux and reasonable draw solute rejection. The effects of the GO loading on the membrane morphology and FO performance of the GO-incorporated TFC membranes are investigated systematically in terms of various characterizations and intrinsic separation performance. The influence of the draw solution concentration is also studied. The GO-incorporated TFC membranes also possess lower fouling propensity in FO test than that without embedded GO.


      PubDate: 2016-01-21T18:21:44Z
       
  • On the scale-up of micro-reactors for liquid–liquid reactions
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): Patrick Plouffe, Michel Bittel, Jonas Sieber, Dominique M. Roberge, Arturo Macchi
      The scale-up of a micro-reactor with a mixer designed for liquid–liquid reactions is investigated using a 3/7th approach that scales the hydraulic diameter at increased flow rates and keeps constant the average rate of energy dissipation. Smaller (d h 283µm) and larger-scale (d h 714µm) mixers are compared using single phase pressure drop measurements and a liquid–liquid reactive extraction. The single phase tests demonstrate that the energy dissipation rate of the larger scale mixer is comparable to the smaller scale mixer at flow rates ~8.5 times greater. The overall volumetric mass transfer coefficients of the reactive extraction, Kca, of both scale mixers were also similar at equal energy dissipation rate in the drop flow regime. Finally, the upper limit of the sizing approach is discussed and compared with commercially available static mixers.
      Graphical abstract image

      PubDate: 2016-01-21T18:21:44Z
       
  • Model-based analysis of water management at anode of alkaline direct
           methanol fuel cells
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): C. Weinzierl, U. Krewer
      Alkaline direct methanol fuel cells (ADMFCs) produce water at the aqueous fed anode. This complicates water management at anode which is analysed in this study by modelling three extreme case scenarios assuming different conditions for water transport or removal. All scenarios include recycling of methanol solution at anode outlet to achieve high methanol efficiencies. One scenario reveals that high operation times and high methanol efficiencies necessitate active stabilisation of anodic water level since both water accumulation and depletion can take place depending on operation conditions. Another scenario shows that water level can be stabilised by adjusting cathodic evaporation and the corresponding water removal from the system. The results indicate that feeding cathode with water-saturated gas is detrimental for stabilising water level. The last scenario suggests the addition of a gas flow to anodic outlet to remove excess water for water level stabilisation. Minimization of additional methanol loss requires to reach high humidities by evaporation. The present paper reveals the impact of processes occurring in ADMFCs on anodic water management and indicates the necessity to quantify water transport through membrane. Knowledge of the influence of operation conditions on water level in the anodic loop are beneficial for design of ADMFC systems.


      PubDate: 2016-01-18T07:41:15Z
       
  • Dynamic interfacial tension in water/n-pentane system: An experimental
           study using the oscillating-jet method
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): Yasuhiko H. Mori
      The interfacial tension working at an interface created by sudden contact of liquid water with saturated common vapors of n-pentane and water under atmospheric pressure (0.101MPa) was experimentally studied, focusing on the behavior of its relaxation to an equilibrium value in response to the progress of the adsorption of n-pentane molecules onto the interface. The oscillating-jet method was used to measure the dynamic interfacial tension, i.e., the interfacial tension varying with time during a short relaxation period (less than 0.1s) after the creation of the interface. It was observed that during the first ~50ms after the creation of the interface, the tension quasi-exponentially decreased from the normal surface-tension value for pure water (70.5mN/m) to the equilibrium value (61.5mNm) which had been obtained in a previous study using the pendant-drop method. An attempt was made to correlate the obtained “interfacial tension versus time” data based on an adsorption/desorption kinetics model.


      PubDate: 2016-01-18T07:41:15Z
       
  • Surfactant flow between a Plateau border and a film during foam
           fractionation
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): Paul Grassia, Sebastian Ubal, Maria Delia Giavedoni, Denny Vitasari, Peter James Martin
      A fluid mechanics problem relevant to foam fractionation processes is analysed. Specifically the fluid flow field transporting surfactant from foam Plateau borders (fed with surfactant-rich material) towards comparatively surfactant-lean foam films is considered. The extent to which this surfactant mass transfer is limited by surface viscous effects is studied. Previous work (Vitasari et al., 2016) made assumptions about the likely flow field along the Plateau border surface. These assumptions suggested that ‘high’ surface viscosity (measured by a suitable dimensionless parameter) led to strong suppression of the rate of surfactant mass transfer from Plateau border to film, whereas ‘low’ surface viscosity did not suppress this mass transfer rate in any significant way. More detailed fluid mechanical calculations which are carried out here corroborate the aforementioned assumptions in the ‘high’ surface viscosity regime. However the calculations suggest that in the ‘low’ surface viscosity regime, in contrast to the findings from the previous assumptions, moderate reductions in the rate of surfactant mass transfer are also possible. Counterintuitively these moderate reductions in mass transfer rate potentially have more negative impact on fractionation processes than the aforementioned strong suppression. This is because they tend to arise under conditions for which the efficiency of the fractionation system is particularly sensitive to any reduction whatsoever in the surfactant mass transfer rate.
      Graphical abstract image Highlights

      PubDate: 2016-01-18T07:41:15Z
       
  • Direct numerical simulations and experiments of a pseudo-2D gas-fluidized
           bed
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): Y. Tang, Y.M. Lau, N.G. Deen, E.A.J.F. Peters, J.A.M. Kuipers
      This paper reports our study on fluidization of 5000 spherical particles in a pseudo-2D gas-fluidized bed by direct numerical simulations (DNS) and experiments as well. Simulations are performed using an immersed boundary method, together with the methodology developed in our earlier work for accurate prediction of gas–solid interactions at relatively low grid resolutions. This modelling approach provides detailed information on the gas flow and the motion of individual particles, which allows for a priori calculation of the bed hydrodynamics. Experimental measurements of solids mean motion are conducted using a combined technique of Particle Image Velocimetry (PIV) and Digital Image Analysis (DIA). Further, the PIV technique is extended and applied for instantaneous measurements of the particle granular temperature, which is the key characteristics of particle velocity fluctuations. For the first time, this paper reports a direct comparison in great detail between DNS results and experimental data for realistic gas fluidization. The detailed comparison reveals a reasonably good agreement with respect to the time-averaged solids motion and the pressure fluctuations. In addition, the granular temperatures calculated from the simulations agree well with the experimental data, but provide more details with respect to the variations corresponding to bubble formation and eruption. From our investigation, it also becomes clear that attention should be paid on the measurement and interpretation of the granular temperature.
      Graphical abstract image Highlights

      PubDate: 2016-01-18T07:41:15Z
       
  • Exergy-based performance analysis of a continuous stirred bioreactor for
           ethanol and acetate fermentation from syngas via Wood–Ljungdahl
           pathway
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): Mortaza Aghbashlo, Meisam Tabatabaei, Ali Dadak, Habibollah Younesi, Ghasem Najafpour
      In this work, a thermodynamic framework was proposed to achieve improved process understanding of ethanol and acetate fermentation in a continuous stirred tank bioreactor from syngas through the Wood–Ljungdahl pathway. The bioreactor performance was evaluated using both conventional exergy and eco-exergy principles to identify the effect of different operational parameters i.e. agitation speeds and liquid media flow rates as well as syngas volume flow rates and its composition on the sustainability and renewability of the process. The exergy efficiency of the bioreactor was found to be in the range of 8.14–89.51% and 8.86–89.52% using the conventional exergy and eco-exergy concepts, respectively. The maximum exergetic productivity index was found to be 6.82 and 6.90 using the conventional exergy and eco-exergy concepts, respectively, at agitation speed of 450rpm, liquid media flow rate of 0.55ml/min, and syngas volume flow rate of 8ml/min containing 10% CO2, 15% Ar, 20% H2, and 55% CO. In general, the exergetic performance parameters computed using both concepts under the studied conditions did not display significant differences because of the low volume of the bioreactor and slow growth rate of the microorganisms. The results of the present study showed that exergy concept and its extensions could undoubtedly play a strategic role in assessing biofuel production pathways with respect to the issues currently of major interest in the renewable energy industry, i.e., sustainability and productively.


      PubDate: 2016-01-14T06:03:57Z
       
  • Application of solute distribution theory to melt crystallization of fatty
           acids
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): Keisuke Fukui, Takuto Fujikawa, Hiroshi Satone, Takuji Yamamoto, Kouji Maeda, Hidetoshi Kuramochi
      To study solute distribution at the solid–liquid (S–L) interface during melt crystallization, we examined the applicability of the interfacial solute distribution factor proposed based on a kinetic model involving both mass and heat balances at the interface. The factor derived from the model was compared with the experimental results obtained by employing a binary melt with the different species and concentrations of fatty acids as biodiesel related mixtures. As a result, we were able to reveal the empirical relation between the purity of the crystal and the solidification conditions of the melt. Based on the model, we also numerically calculated the transient changes in the interfacial solute distribution factor as well as the temperature of the S–L interface in the solidification process of the melt. The minimization of the factor was confirmed when the melt was supercooled at the S–L interface after starting solidification.


      PubDate: 2016-01-14T06:03:57Z
       
  • Slope curve method for the analysis of separations in extraction columns
           of infinite height
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): J. Burger, M. Kaul, H. Hasse
      A new method for the conceptual design of counter-current extraction columns, the slope curve method (SCM), is presented. It is a graphical method based on the equilibrium stage model and developed here for ternary mixtures. The well-known stage-to-stage construction in the ternary phase diagram is replaced by a concise representation in the so-called slope diagram. In that diagram, the slope curve represents the tie lines and operating lines represent material balances. Infinite column height is assumed so that for given feed and solvent composition, the only remaining degree of freedom is the solvent-to-feed ratio. Varying that parameter, all feasible solutions are obtained in the slope diagram. The corresponding product compositions can be reconstructed. Using the method, it is readily shown that internal pinches only occur for certain classes of mixtures, which can be readily identified based on an analysis of the shape of the slope curve. As the SCM yields a complete survey of all feasible solutions it is particularly suited for feasibility studies in conceptual design as well as for obtaining general insights in extractive separations.


      PubDate: 2016-01-14T06:03:57Z
       
  • Design of microchannel Fischer–Tropsch reactor using cell-coupling
           method: Effect of flow configurations and distribution
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): Seongho Park, Ikhwan Jung, Yongkyu Lee, Krishnadash S. Kshetrimayum, Jonggeol Na, Seongeon Park, Seolin Shin, Daegeun Ha, Yeongbeom Lee, Jongtae Chung, Chul-Jin Lee, Chonghun Han
      The objective of this study is to design a microchannel Fischer–Tropsch reactor with the evaluation of several flow configurations and distribution effect. A cell coupling computation was carried out for the microchannel reactor of five different flow configurations. In the cell coupling method, all the process and cooling channels are decomposed into a number of unit cells, and then coupled to solve the material and energy balances. The realistic flow distribution effect was incorporated into the model by using results obtained from computational fluid dynamics (CFD). The kinetic model was validated with experimental data, and the results of the reactor model was compared with data taken from the literature and the results were found to be in good agreement. Several case studies were conducted to see the effect of flow configurations, flow distribution, and catalyst loading zones. It was observed that the geometry of cross-co-cross current was found to give the best performance among the designs considered. The study also reveals that flow distribution and catalyst loading zone need to be carefully controlled for the safe, robust, and reliable reactor design and operation.


      PubDate: 2016-01-14T06:03:57Z
       
  • Investigation of emulsification in static mixers by optical measurement
           techniques using refractive index matching
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): Richard Häfeli, Oliver Rüegg, Marco Altheimer, Philipp Rudolf von Rohr
      This study compares a two-phase flow through a foam-like porous structure and a Sulzer SMXTM static mixing element. Refractive index matching between two immiscible fluids and the internal structures enables optical measurements to be performed. The droplet size and position within the internal structures were observed by laser-induced fluorescence. The results show that at low flowrates, droplets follow preferred paths, whereas at higher flowrates, they are more homogeneously distributed within the structures. The droplet size distribution was found to be well represented by the Sauter mean diameter. Measuring along the axis of the two static mixers, we found that droplets disintegrate more quickly in the foam-like porous structure. As both geometries have the same porosity and hydraulic diameter, we conclude that the change in the free cross section is also an important parameter. We observed that in the geometry with large changes in the free cross section, the droplets are smaller.
      Graphical abstract image Highlights

      PubDate: 2016-01-14T06:03:57Z
       
  • Enhancing catalyst effectiveness by increasing catalyst film thickness in
           coated-wall microreactors: Exploiting heat effects in catalytic methane
           steam micro-reformers
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): Holly Butcher, Benjamin A. Wilhite
      The potential for increasing endothermic reforming process capacity of a heat-exchanger microreactor without compromising thermal or catalyst efficiency via employing unconventionally-thick catalyst washcoatings is investigated. This is achievable through exploiting the “internal” heating of the catalyst film, i.e. existence of a non-zero heat flux at the wall-catalyst interface at the inner boundary of the film, which is a characteristic of the heat-exchanger microreactor design. Classical one-dimensional analysis of non-isothermal reaction and diffusion in an internally-heated catalyst film identifies minimum values for Prater Temperature and dimensionless activation energy required for internal accumulation of applied heat to be effectively utilized. Under such conditions, analysis confirms the existence of a range of Thiele Moduli, or catalyst film thicknesses, corresponding to complete utilization of internally-supplied heat at catalyst effectiveness greater than unity. Subsequent application of these design rules to a previously validated computational fluid dynamic (CFD) model of an industrial annular micro-channel reformer (AMR) for methane steam reforming confirm that increasing catalyst film thicknesses to values corresponding to Thiele Modulus greater than unity enables intensification of the microreactor performance via increasing reforming capacity while maintaining equivalent thermal efficiency and retaining competitive catalyst effectivenesses.


      PubDate: 2016-01-14T06:03:57Z
       
  • Visualization of the trapping of inertial particles in a laminar mixing
           tank
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): Steven Wang, Robert L Stewart, Guy Metcalfe
      We report on new methods and results for the trajectory visualization and tracking of large inertial particles in a laminar (chaotic) mixing tank. Using specially designed light-emitting capsules, particle orbits were visualized using streak photography to reveal pathlines of capsules moving in the laminar fluid flow. We present visualization results on unexpected trapping of particles whereby finite-sized particles/capsules can spontaneously localize into the vortex tubes in the laminar stirred system. Once into tubes, large inertial particles move in helical orbits as do passive particles. Mixing tanks have been in use over a number of centuries but this trapping phenomenon has been consistently ignored. We also measure the three-dimensional position of large inertial particles over time using an externally positioned camera and planar mirror in a calibrated setup. As the light capsules used in this study give very high contrast even when the fluid is murky, the work provides a sound basis for further research development of measurement techniques for large (industrial) scale flows.


      PubDate: 2016-01-14T06:03:57Z
       
  • Sliding mode control design for a rapid thermal processing system
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): Tengfei Xiao, Han-Xiong Li
      A sliding mode control strategy is developed for temperature control of a rapid thermal processing (RTP) system to enhance temperature accuracy and uniformity when heating in this work. Temperature dynamics of the RTP is nonlinear and infinite-dimensional while order of the controller should be finite due to implementation limitations. Developing a nonlinear low-order controller for the system is important if accurate and uniform control of the temperature is required. This work addresses this issue by developing a sliding mode controller based on the dominant modes of the system. The schemes are applied to a RTP system and excellent performances are achieved.


      PubDate: 2016-01-14T06:03:57Z
       
  • Operability coating window of dual-layer slot coating process using
           viscocapillary model
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): Ho Suk Ji, Won-Gi Ahn, Ilyoung Kwon, Jaewook Nam, Hyun Wook Jung
      The viscocapillary model for predicting the operability windows in a dual-slot coating process for two Newtonian liquids has been derived by means of a lubrication approximation technique from two-dimensional (2-D) Navier-Stokes equations. The flow rates per width and the pressure differences simplified in several sub-regions within the coating bead regime have been integrated together with approximations of the upstream and downstream menisci and the interlayer between the top and bottom layers. Coating limits or onsets for leaking and bead break-up defects have been determined on the basis of the position of upstream meniscus of the bottom layer as an indicator. Operability coating windows predicted from the viscocapillary model show a good agreement with those by 2-D CFD solver and experiments. In addition, the pressure profiles within the coating bead regime compared between the viscocapillary and 2-D models are qualitatively similar. This simplified model can be applied as a fast tool for usefully manipulating the stable operations in dual-layer slot coating systems.


      PubDate: 2016-01-14T06:03:57Z
       
  • Impact of suspended solids on Fr 13 failure of UV irradiation for
           inactivation of Escherichia coli in potable water production with
           turbulent flow in an annular reactor
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): Nadiya Abdul-Halim, Kenneth R. Davey
      Ultraviolet irradiation (UV) is an important alternative to disinfection for production of potable water. Viable Escherichia coli is a widely used indicator for public health risk. However, UV efficacy is reduced by suspended solids that can act as both UV shielding and UV absorbing, agents. Failure of UV irradiation can lead to an enduring health legacy. Here the probabilistic Fr 13 methodology of Davey et al. (2015) is demonstrated for turbulent flow of feed water with suspended solids irradiated in an annular reactor and, a comparison made with the traditional deterministic method. The aim was to examine the impact of naturally occurring fluctuations in suspended solids concentration on failure to inactivate viable E. coli. A UV failure factor (p) is defined in terms of the design and actual log10 reduction in viable E. coli. UV irradiation is simulated using (Latin Hypercube) Monte Carlo sampling. Illustrative overall results show some 32.1% and 43.7% of apparent successful operations could unexpectedly fail over the long term due, respectively, to combined impact of random fluctuations in feed water flow (Q), lamp intensity (I 0) and shielding and absorption of UV by suspended solids [conc]. This translates to four (4) failures each calendar month (the comparison rate without suspended solids is 16% or two (2) failures per month). An unexpected finding however is, although the initial presence of suspended solids as both UV shielding (median particle size 23μm) and absorbing agent has a highly significant impact on reducing UV efficacy, fluctuations in concentration of these in the feed water do not meaningfully impact overall vulnerability. UV failure is impacted highly significantly by fluctuation in feed water flow. It is concluded this is strong quantitative evidence to emphasize that solids should be removed prior to the UV reactor, and that an improved flow control be used to reduce variance on feed water flow, rather than increased UV dose. This work will be of benefit to operators of UV equipment and researchers in risk analyses.
      Graphical abstract image

      PubDate: 2016-01-14T06:03:57Z
       
  • Dynamics and stability analysis of gas-phase bulk polymerization of
           propylene
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): Lei Luo, Nan Zhang, Zhi Xia, Tong Qiu
      As one of the most important downstream products of propylene, polypropylene (PP) plays a key role in industrial production and our daily life. In this paper, a detailed mechanism model is built which is derived from practical data and bifurcation diagrams are also obtained to assess an open-loop stability analysis of the reactor, finding out the existence of Hopf point which leads to instability of the open-loop system. Since temperature runaway and oscillations resulted from unstable operation and Hopf point could pose a threat to the safety, productivity and quality of the production process, PI controller is introduced to the system and forms a closed-loop system to improve the stability and controllability of the system. Further calculation shows that, in the case of PI control, the Hopf point, which is the dividing point of the stable and unstable region on the parameter plane, not vanishes but moves to another position with higher catalyst feed rate and the risk of instability still remains. In this situation, appropriate controller parameters can be helpful to avoid unstable operation and expand the range of stable region. Additionally, in the latter part of our work, different closed-loop dynamic simulations are also conducted to show how stability index and the imaginary part of eigenvalues affect the dynamic behaviors of the closed-loop system. In general, this work mainly focuses on the relationship between the process stability and controller parameters and the outcomes are expected to be a guide for industrial operation and design of control system.


      PubDate: 2016-01-10T06:02:38Z
       
  • Synthesis of hydroxymethylfurfural from cellulose using green processes: A
           promising biochemical and biofuel feedstock
    • Abstract: Publication date: 13 March 2016
      Source:Chemical Engineering Science, Volume 142
      Author(s): Prasant Kumar Rout, Ashween Deepak Nannaware, Om Prakash, Alok Kalra, Ram Rajasekharan
      Inedible, lignocellulosic biomass has been recognized as most promising renewable resource for the production of high value bio-chemicals. The pretreated biomass or isolated cellulose is a biopolymer of glucose used as a stating material for the synthesis of 5-hydroxymethylfurfural (HMF). HMF is listed among the top 10 bio-based chemicals by USA Department of Energy and it acts as feedstock for deriving a number of commodity products (Bonzell and Petersen, 2010, Green Chem. 12, 539). In present review, we have systematically summarized the catalytic reaction for the synthesis of HMF from pretreated biomass/isolated cellulose using green processes. Further, through catalytic approach, HMF is translated into industrial important chemicals (2,5-diformylfuran, furan-2,5-dicarboxylicacid, 2,5-furandimethanol, furfuraylalcohol, etc) or high calorific value biofuel (2,5-dimethylfuran, 2,5-dimethyltetrahydrofuran, 2,5-bis(alkoxymethyl)furans, etc). In the profitable scale of HMF production, levulinic acid (LA) is generated as a major byproduct. Besides HMF, this review also outlines the catalytic strategy for the conversion of LA to industrially important chemicals along with the biofuel additives. Finally, the bio-toxicity of synthesized chemicals, which connected into different functional groups have been summarized to meet the criteria of the green technology for commercialization.
      Graphical abstract image

      PubDate: 2016-01-10T06:02:38Z
       
  • Hydrodynamics of novel structured packings: An experimental and
           multi-scale CFD study
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): Qunsheng Li, Tao Wang, Chengna Dai, Zhigang Lei
      Three types of structured packings with wave-like corrugated sheets were investigated, aiming to improve the hydrodynamics of structured packings. The experimental results showed that the new proposed structured packings have a significant advantage in pressure drop and capacity over traditional Mellapak 125X. A modified multi-scale CFD (computational fluid dynamic) model was applied to characterize the hydrodynamic performance of the novel packings. At the micro-scale (corrugation scale), a 2D VOF (volume of fluid) model was used to trace the gas–liquid interface and to calculate the liquid film thickness for two-phase flow; then, a 3D VOF model was used to calculate the effective wetting area at the meso-scale (packing element scale). Finally, a 3D porous media model was proposed to calculate the dry and wet pressure drops at the macro-scale (column scale). The average relative deviations between the experimental data and the calculated results for dry and wet pressure drops were 7.26% and 8.24%, respectively, confirming validity of the CFD simulations. The proposed modified multi-scale CFD model can be used effectively to design and optimize complex structured packings.


      PubDate: 2016-01-10T06:02:38Z
       
  • Macrocyclic β-cyclodextrin derivative-based aqueous-two phase
           systems: Phase behaviors and applications in enantioseparation
    • Abstract: Publication date: 2 April 2016
      Source:Chemical Engineering Science, Volume 143
      Author(s): Jun Wang, Hua Yang, Jingang Yu, Xiaoqing Chen, Feipeng Jiao
      In this work, three macrocyclic β-cyclodextrin (β-CD) derivatives, namely carboxymethyl-β-cyclodextrin (CM-β-CD), sulfobutyl ether-β-cyclodextrin (SBE-β-CD), and hydroxypropyl-β-cyclodextrin (HP-β-CD), were employed in the formation of novel aqueous two-phase system (ATPS) with several hydrophilic solvents respectively. It was observed that anionic β-CD derivatives (CM-β-CD and SBE-β-CD) facilitated the ATPS formation and the obtained binodal curves showed a decreasing order in inducing ATPS as acetonitrile≈1-propanol>2-propanol>ethanol. Furthermore, the proposed ATPS as a novel enantioselective liquid–liquid extraction technique was evaluated by enantioseparating racemic zopiclone (ZPC). Opposite partitioning orientations for ZPC in two groups of the investigated ATPS were studied systematically and 1-propanol/CM-β-CD ATPS was selected as the optimal enantioseparation system. Under the optimal conditions, moderate enantioseparation efficiency (α=2.58 and e.e.%=32.66%) and high recovery (R T(S) =95.54% and R T(R) =98.22%) were achieved simultaneously via a single run of extraction.


      PubDate: 2016-01-10T06:02:38Z
       
  • Simulation of droplet breakage in turbulent liquid–liquid
           dispersions with CFD-PBM: Comparison of breakage kernels
    • Abstract: Publication date: 13 March 2016
      Source:Chemical Engineering Science, Volume 142
      Author(s): Zhengming Gao, Dongyue Li, Antonio Buffo, Wioletta Podgórska, Daniele L. Marchisio
      In this work droplet breakage in turbulent liquid–liquid dispersions is simulated by using computational fluid dynamics and population balance modelling. Model predictions are validated against experimental data for eight test cases, namely stirred tanks with different geometries and different continuous and disperse phases. The two first test cases correspond to two geometrically similar stirred tanks (one being the scale up of the other) working under the same power input per unit mass with water as continuous phase and a mixture of chlorobenzene and toluene as disperse phase. The last six test cases correspond to a slightly different geometry, working with water as continuous phase and different silicon oils as disperse phase, characterized by different viscosity values, stirred at different stirring rates. Simulations are performed with our implementation of the quadrature method of moments for the solution of the population balance model into the open-source computational fluid dynamics code OpenFOAM. Two different breakage kernels are considered in this work, based respectively on the classical homogeneous and multifractal turbulence theories. Analysis of the kernels and comparison with experiments reveal that the second kernel results is better agreement with experiments, a more accurate description of the underlying physics and presents the additional advantage of having no fitting constants.
      Graphical abstract image Highlights

      PubDate: 2016-01-01T20:45:31Z
       
  • Model-based real-time optimisation of a fed-batch cyanobacterial hydrogen
           production process using economic model predictive control strategy
    • Abstract: Publication date: 13 March 2016
      Source:Chemical Engineering Science, Volume 142
      Author(s): Ehecatl Antonio del Rio-Chanona, Dongda Zhang, Vassilios S. Vassiliadis
      Hydrogen produced by microorganisms has been considered as a potential solution for sustainable hydrogen production for the future. In the current study, an advanced real-time optimisation methodology is developed to maximise the productivity of a 21-day fed-batch cyanobacterial hydrogen production process, which to the best of our knowledge has not been addressed before. This methodology consists of an economic model predictive control formulation used to predict the future experimental performance and identify the future optimal control actions, and a finite-data window least-squares procedure to re-estimate model parameter values of the on-going process and ensure the high accuracy of the dynamic model. To explore the efficiency of the current optimisation methodology, effects of its essential factors including control position, prediction horizon length, estimation window length, model synchronising frequency, terminal region and terminal cost on hydrogen production have been analysed. Finally, by implementing the proposed optimisation strategy into the current computational fed-batch experiment, a significant increase of 28.7% on hydrogen productivity is achieved compared to the previous study.


      PubDate: 2016-01-01T20:45:31Z
       
  • 3D numerical simulation of a lab-scale pressurized dense fluidized bed
           focussing on the effect of the particle-particle restitution coefficient
           and particle–wall boundary conditions
    • Abstract: Publication date: 13 March 2016
      Source:Chemical Engineering Science, Volume 142
      Author(s): Pascal Fede, Olivier Simonin, Andrew Ingram
      3D numerical simulations of dense pressurized fluidized bed are presented. The numerical prediction of the mean vertical solid velocity are compared with experimental data obtained from Positron Emission Particle Tracking. The results show that in the core of the reactor the numerical simulations are in accordance with the experimental data. The time-averaged particle velocity field exhibits a large-scale toroidal (donut shape) circulation loop. Two families of boundary conditions for the solid phase are used: rough wall boundary conditions (Johnson and Jackson, 1987 and No-slip) and smooth wall boundary conditions (Sakiz and Simonin, 1999 and Free-slip). Rough wall boundary conditions may lead to larger values of bed height with flat smooth wall boundary conditions and are in better agreement with the experimental data in the near-wall region. No-slip or Johnson and Jackson׳s wall boundary conditions, with sufficiently large value of the specularity coefficient ( ϕ ≥ 0.1 ) , lead to two counter rotating macroscopic toroidal loops whereas with smooth wall boundary conditions only one large macroscopic loop is observed. The effect of the particle-particle restitution coefficient on the dynamic behaviour of fluidized bed is analysed. Decreasing the restitution coefficient tends to increase the formation of bubbles and, consequently, to reduce the bed expansion.
      Graphical abstract image Highlights

      PubDate: 2015-12-28T20:39:27Z
       
  • Mechanical behaviour of micro-capsules and their rupture under compression
    • Abstract: Publication date: 13 March 2016
      Source:Chemical Engineering Science, Volume 142
      Author(s): Ali Ghaemi, Alexandra Philipp, Andreas Bauer, Klaus Last, Andreas Fery, Stephan Gekle
      Understanding the deformation of micro-capsules (MCs) and especially the mechanism of their rupture is of crucial importance for their performance in various applications. Mechanical instability can on the one hand be a failure mechanism, resulting in undesired release, but can on the other hand be used as a release trigger. In this work, finite element analysis together with nano-indentation experiments is applied to characterize the deformation of single filled MCs made of melamin–formaldehyde. The simulations reveal that the capsules undergo different deformation regimes: starting from linear elastic deformation, upon further compression the MCs yield and are plastically deformed. The final step is a strain hardening regime, where the maximum stress rapidly increases till the MCs rupture. Finally, we describe the MCs rupture mechanism obtained from numerical simulation and experimental results. We show that the axial and radial stresses cause significant thinning of the shell at the MC׳s equator, and that the circumferential stress leads to rupture along the meridians of the MC.


      PubDate: 2015-12-24T20:35:15Z
       
  • Block length determines the adsorption dynamics mode of triblock
           copolymers to a hydrophobic surface
    • Abstract: Publication date: 13 March 2016
      Source:Chemical Engineering Science, Volume 142
      Author(s): Yisheng Xu, Kaihang Shi, Shuangliang Zhao, Xuhong Guo, Jie Wang
      Many material processes including surface modification and material fabrication depend on the mechanism by which polymers are adsorbed onto solid/liquid interfaces. Although the morphologies of block copolymers near the interface have been extensively investigated, the understanding of the adsorption dynamics is still limited. Here, we show that the block length determines the dynamic adsorption mode under conditions beyond the critical micelle concentration (CMC). The adsorption kinetics are investigated using in situ experimental characterization combined with Dissipative Particle Dynamics simulations. Two types of symmetrical triblock copolymers, i.e., PEO–PPO–PEO, with different hydrophilic PEO block lengths are studied. While both types of copolymers present similar adsorption dynamics at concentrations below the CMC, their dynamic adsorption modes are distinct at concentrations above the CMC. The present experimental–numerical study provides a mechanistic interpretation of this difference, which casts helpful insight for the dynamic control process of surface modification and material fabrication.


      PubDate: 2015-12-24T20:35:15Z
       
  • Upscaling diffusion and reaction processes in multicellular systems
           considering different cell populations
    • Abstract: Publication date: 13 March 2016
      Source:Chemical Engineering Science, Volume 142
      Author(s): Raquel de los Santos-Sánchez, Francisco J. Valdés-Parada, Yolanda I. Chirinoz
      In this work, we derive a mass equilibrium model to describe the diffusion and reaction processes in a cell cluster composed of different cell populations. This study extends previous ones in which the existence of only one type of cell population was considered. The microscopic description is used to derive an upscaled model for diffusion and reaction in multicellular systems using the method of volume averaging. The effective diffusivity coefficient that appears in the upscaled equation is predicted by solving a closure problem in simple 2D unit cells. This effective coefficient depends on the volumetric fraction of the cells, the cell distribution, and the ratios of microscopic diffusivities, permeabilities and solubilities that measure the differences between the physical properties of living cells. It was found that there is a wide range of these parameter values in which the effect of considering different cell populations is important, leading to errors in the predictions of the effective diffusivity with respect to those resulting from assuming that there is only one type of cell population.


      PubDate: 2015-12-24T20:35:15Z
       
  • Prediction of the liquid film distribution in stratified-dispersed
           gas–liquid flow
    • Abstract: Publication date: 13 March 2016
      Source:Chemical Engineering Science, Volume 142
      Author(s): M. Bonizzi, P. Andreussi
      A mathematical model for predicting the circumferential liquid film distribution in stratified-dispersed flow is presented. Objective of the model is to describe the typical flow conditions of wet gas transportation in long, near-horizontal pipelines. In these applications, depending on the gas velocity and pipe diameter, a large asymmetry of the liquid film distribution may arise. The model is based on the assumption that in stratified-dispersed flow, liquid droplets can only be entrained by the gas from the thick liquid layer flowing at pipe bottom. It is also assumed that the deposition of smaller droplets is related to an eddy diffusivity mechanism and regards the entire pipe circumference, while larger droplets deposit by gravitational settling on the pipe bottom. These assumptions explain the formation of a thin, non-atomizing film in the upper part of the pipe. The presence and flow structure of this film appreciably affect the pressure gradient and the liquid hold-up in the pipe and are of great importance in flow assurance studies. The model has been validated against i) the experimental observations recently published by Pitton et al. (2014), the data collected by ii) Laurinat (1982), iii) Dallman (1978), and iv) the predictions of three-dimensional CFD simulations conducted by Verdin et al. (2014). It is shown that the relevant mechanisms which are responsible for the liquid film distribution are the gravitational film drainage, droplet entrainment/deposition and wave spreading. In particular, at high gas velocities and/or small pipe diameters, the asymmetry of the liquid film diminishes owing to the wetting mechanism of wave spreading which makes the distribution of the film more uniform in the circumferential direction. As the gas velocity diminishes and/or for larger pipe diameters, wave spreading is less effective and for these flow conditions only gravitational drainage and droplet entrainment/deposition are responsible for the more asymmetric shape of the liquid film.


      PubDate: 2015-12-24T20:35:15Z
       
  • Amino-impregnated MOF materials for CO2 capture at post-combustion
           conditions
    • Abstract: Publication date: 13 March 2016
      Source:Chemical Engineering Science, Volume 142
      Author(s): Fernando Martínez, Raúl Sanz, Gisela Orcajo, David Briones, Víctor Yángüez
      Three different commercial Metal-Organic Frameworks (HKUST-1, MIL-53(Al) and ZIF-8) were modified by wetness impregnation of tetraethylenepentamine (TEPA) molecules. These amino-containing MOF materials were studied in CO2 adsorption under post-combustion conditions (45°C and 1bar) using a simulated exhausted flue gas stream of power plants (75% inert gas; 5% O2; 14% CO2; 6% H2O; % in vol.). The yield of TEPA incorporation was significantly affected by the physicochemical properties of the MOF precursors. The presence of reactive sites of HKUST-1 (unsaturated copper sites) or MIL 53(Al) (exposed hydroxyl bridges (µ2-OH)) as well as their worst textural properties as compared to ZIF-8,led to lower TEPA loadings and porosities of the resultant amino-impregnated HKUST-1 and MIL 53(Al) materials. The ZIF-8 material showed a better distribution of TEPA since reactive surface sites are not present in this support with a higher superficial development. Amino-impregnated ZIF-8 samples exhibited enhanced adsorption capacities by combination of physical and chemical adsorption of CO2 over the TEPA-impregnated microporous framework. The increase of the TEPA content in the ZIF-8 material led to CO2 uptake up to 67mgCO 2/gads using pure CO2 at 0.15bar and 45°C. Under post-combustion CO2 capture conditions, TEPA-impregnated ZIF-8 samples underwent a remarkable increase of the carbon dioxide uptake up to 104mgCO2/gads, due to the presence of moisture, which is responsible of increasing the CO2 capture efficiency of amino groups. After several adsorption/desorption cycles at post-combustion adsorption conditions, TEPA-containing ZIF-8 samples have shown a high structural stability, maintaining the CO2 uptake practically constant.
      Graphical abstract image

      PubDate: 2015-12-21T08:22:51Z
       
  • Modeling of the biomass combustion on a forward acting grate using XDEM
    • Abstract: Publication date: 13 March 2016
      Source:Chemical Engineering Science, Volume 142
      Author(s): Amir Houshang Mahmoudi, Xavier Besseron, Florian Hoffmann, Miladin Markovic, Bernhard Peters
      The grate firing system is one of the most common ways for the combustion of biomass because it is able to burn a broad range of fuels with only little or even no requirement for fuel preparation. In order to improve the fuel combustion efficiency, it is important to understand the details of the thermochemical process in such furnaces. However, the process is very complex due to many involved physical and chemical phenomena such as drying, pyrolysis, char combustion, gas phase reaction, two phase flow and many more. The main objective of this work is to study precisely the involved processes in biomass combustion on a forward acting grate and provide a detailed insight into the local and global conversion phenomena. For this purpose, XDEM as an Euler–Lagrange model is used, in which the fluid phase is a continuous phase and each particle is tracked with a Lagrangian approach. The model has been compared with experimental data. Very good agreements between simulation and measurement have been achieved, proving the ability of the model to predict the biomass combustion under study on the grate.


      PubDate: 2015-12-21T08:22:51Z
       
  • Influence of operating parameters and flow regime on solid dispersion
           behavior in a gas–solid spout-fluid bed
    • Abstract: Publication date: 13 March 2016
      Source:Chemical Engineering Science, Volume 142
      Author(s): Shiliang Yang, Yuhao Sun, Jingwei Wang, Andy Cahyadi, Jia Wei Chew
      The dispersion behavior of the solid phase in a three-dimensional spout-fluid bed was numerically investigated via the approach of coupled computational fluid dynamics and discrete element method (CFD–DEM), in which the fluid and solid phases were solved using the Eulerian and Lagrangian framework, respectively. Detailed trends of both the local and overall dispersion behaviors of the solid phase in the system were quantitatively studied, and the impact of various operating parameters (namely, spouting gas velocity (U sp ), background velocity (U bg ), particle diameter (d p ), the bed depth (L) and bed height) and flow regime on lateral and vertical solid dispersion was investigated. The results show that varying U sp , U bg and d p affects the local solid dispersion in the spout and fountain regions more than the annulus. To enhance the overall solid dispersion, either U sp or U bg or L can be increased, or d p and bed height can be decreased. Meanwhile, the total gas flow rate plays the dominated role for overall dispersion of solid phase. Finally, solid dispersion is the most effective in the Jet-in-fluidization regime, followed by the Spouting-with-aeration then the Intermediate/spout-fluidization regimes.


      PubDate: 2015-12-21T08:22:51Z
       
  • Pair interactions between conducting and non-conducting cylinders under
           uniform electric field
    • Abstract: Publication date: 13 March 2016
      Source:Chemical Engineering Science, Volume 142
      Author(s): Huicheng Feng, Teck Neng Wong
      This paper analytically studies pair interactions between a conducting and a non-conducting cylinder with uniform electric fields imposed in two basic ways: perpendicular and parallel to the connection line of the two cylinder centers. The results show that electroosmosis and induced charge electroosmosis are generated on the non-conducting and conducting cylinders, respectively. Moreover, the nonuniform local electric field and the corresponding asymmetric fluid flow drive the cylinders into motion: both translating and rotating under the perpendicular applied electric field, while solely migrating along the x-axis under the parallel applied electric field. The velocity component due to electrostatic force is negligible compared to that due to electrophoresis or induced charge electrophoresis. Since the pair interactions reduce as the distance between cylinders increases, the cylinder velocities decrease accordingly. Under the perpendicular applied electric field, the cylinders repel each other along the x-axis; the motion direction along the y-axis as well as the direction of rotational velocity depends on the sign of the zeta potential of non-conducting cylinder. Under the parallel applied electric field, the cylinders repel each other when the zeta potential of non-conducting cylinder is positively very small or negative, while they attract each other when the zeta potential is positively large.


      PubDate: 2015-12-21T08:22:51Z
       
  • Antifouling PVDF membrane prepared by VIPS for microalgae harvesting
    • Abstract: Publication date: 13 March 2016
      Source:Chemical Engineering Science, Volume 142
      Author(s): Antoine Venault, Melibeth Rose B. Ballad, Yu-Tzu Huang, Yi-Hung Liu, Chi-Han Kao, Yung Chang
      Provided the use of a water-insoluble modifier, in-situ modification of PVDF membranes is an ideal method for preparing low-biofouling membranes. We report the formation, characterization and low-biofouling performances of modified PVDF membranes prepared by vapor-induced phase separation for microalgae harvesting. Poly(styrene)-b-poly(ethylene glycol) methacrylate (PS-b-PEGMA) is used as antifouling material. After characterizing the physico-chemical properties of membranes by SEM, AFM, FT-IR, XPS, and tensile tester, their hydrophilicity was assessed. Hydration capability was importantly enhanced with copolymer content. Adsorption of bovine serum albumin (BSA), lysozyme (LY) and fibrinogen (FN) was tested to investigate the resistance of membranes to nano-biofouling. Best results were obtained with membrane prepared from a casting solution containing 4wt% copolymer (PS-b-PEGMA-4). Bacterial attachment tests proved that membranes could also resist micro-biofouling. Flux recovery ratio after filtration of BSA with PS-b-PEGMA-4 membrane was higher than with a commercial hydrophilic PVDF membrane. Applied in microalgae harvesting, it was found that membranes could efficiently resist biofouling by microalgae (FRR=76.9% with PS-b-PEGMA-4), still enabling a rejection ratio over 99.7%.


      PubDate: 2015-12-21T08:22:51Z
       
  • The controlled growth of calcium sulfate dihydrate (gypsum) in aqueous
           solution using the inhibition effect of a bubble column evaporator
    • Abstract: Publication date: 13 March 2016
      Source:Chemical Engineering Science, Volume 142
      Author(s): Chao Fan, Richard M. Pashley
      Chemical precipitation is a widely used method to synthesize sparingly soluble salts for inorganic materials production. A bubble column evaporator (BCE) process was used to precipitate calcium sulfate (as CaSO4·2H2O) from the reaction of calcium chloride and potassium sulfate solutions, at different degrees of supersaturation. In the BCE system, fine bubbles are continuously produced as a warm dry gas is pumped into a column of solution through a porous sinter. This process was used here as the basis for a new approach to control precipitation with uniform mixing and continuous concentration through rapid water vapor transfer. In this study it was found that the BCE process, compared to simple stirring and even the quiescent solution, had a significant inhibition effect on the induction of precipitation and reduced the growth rate of the precipitate. This precipitation control facilitates the collection of particles over a wide range from nanometer to micrometer size. In the BCE process, the early stage of CaSO4 precipitated onto the surface of nano-sized silica spheres was characterized using dynamic light scattering, zeta potential analysis and atomic force microscopy imaging, which indicated that a coating was produced on the silica surface. The inhibition effect observed with the BCE process suggests that it could be used for controlled precipitate growth and also for the de-watering or concentration of industrial wastewater prior to disposal.
      Graphical abstract image

      PubDate: 2015-12-21T08:22:51Z
       
  • Evidence for immobile transitional state of water in methane clathrate
           hydrates grown from surfactant solutions
    • Abstract: Publication date: 13 March 2016
      Source:Chemical Engineering Science, Volume 142
      Author(s): Jeffrey D. Botimer, Derek Dunn-Rankin, Peter Taborek
      We report studies of the kinetics of growth of methane hydrate from liquid water containing small amounts of surfactant ( < 500 ppm of sodium dodecyl sulfate, SDS). The kinetics are monitored using simultaneous measurements of the uptake of methane detected by a pressure drop in the gas phase, and either visual observations of the amount of liquid water and solid phase in the reaction vessel, or in situ micro-Raman measurements or in situ NMR measurements. These diagnostics show that the uptake of methane and the conversion of liquid water to a solid phase do not occur simultaneously; the uptake of gas always lags the visual and spectroscopic signatures of the disappearance of liquid water and the formation of solid. The evidence suggests that the SDS causes water to form an intermediate immobile solid-like state before combining with the methane to form hydrate. This growth mechanism is related to the surfactant and disappears for low SDS concentrations ( < 25 ppm ) .


      PubDate: 2015-12-21T08:22:51Z
       
  • Sono-chemiluminescence (SCL) in a high-pressure double stage
           homogenization processes
    • Abstract: Publication date: 13 March 2016
      Source:Chemical Engineering Science, Volume 142
      Author(s): Marc Schlender, Katharina Minke, Heike P. Schuchmann
      An applied back-pressure to a high pressure homogenization system influences the development of hydrodynamic cavitation and the collapse of cavitation bubbles. This paper focuses on the effect of back-pressure on hydrodynamic cavitation and how the intensity of collapsing cavitation bubbles can be identified. Based on sono-chemiluminescence (SCL), an optical measuring method was developed to detect cavitation induced formation of •OH radicals, which indicates the intensity of collapsing cavities. The results are discussed with the introduced dimensionless SCL intensity number I ¯ SCL . The I ¯ SCL number increases with increasing inlet pressure as well as with increasing back-pressure and confirms therewith theoretical based assumptions by other studies. A maximum I ¯ SCL at a back-pressure of approximately 30% was found and reduced to an intensified collapse of cavities in or after the first high pressure disruption unit. The maximum in SCL intensity is in line with the minimum droplet size of corresponding emulsification experiments.


      PubDate: 2015-12-17T08:18:25Z
       
 
 
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